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Summation

About: Summation is a research topic. Over the lifetime, 954 publications have been published within this topic receiving 45593 citations. The topic is also known as: summation & sum of a sequence.


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Journal ArticleDOI
05 Dec 2017-eLife
TL;DR: It is shown that serotonin (5HT), which is known to regulate gamma power, acts via 5HT2A receptors to suppress an inward-rectifying potassium conductance in FSIs, leading to depolarization, increased input resistance, enhanced spiking, and slowed decay of excitatory post-synaptic potentials (EPSPs).
Abstract: The medial prefrontal cortex plays a key role in higher order cognitive functions like decision making and social cognition. These complex behaviors emerge from the coordinated firing of prefrontal neurons. Fast-spiking interneurons (FSIs) control the timing of excitatory neuron firing via somatic inhibition and generate gamma (30-100 Hz) oscillations. Therefore, factors that regulate how FSIs respond to gamma-frequency input could affect both prefrontal circuit activity and behavior. Here, we show that serotonin (5HT), which is known to regulate gamma power, acts via 5HT2A receptors to suppress an inward-rectifying potassium conductance in FSIs. This leads to depolarization, increased input resistance, enhanced spiking, and slowed decay of excitatory post-synaptic potentials (EPSPs). Notably, we found that slowed EPSP decay preferentially enhanced temporal summation and firing elicited by gamma frequency inputs. These findings show how changes in passive membrane properties can affect not only neuronal excitability but also the temporal filtering of synaptic inputs.

35 citations

Journal ArticleDOI
TL;DR: It is postulated that spatial summation occurs in the central nervous system of humans in view of the characteristics ascribed to the thermosensory apparatus in humans.
Abstract: The possibility of spatial summation of conducted −‡Ts (temperature decrements from the adapted skin temperature) was tested when the −‡Ts were presented simultaneously and individually at symmetrical sites on either side of the body. The use of a signal detection rating method yielded data that indicate that spatial summation is complete (area and intensity trade reciprocally) for −‡s near threshold and at clearly suprathreshold intensities of stimulation is invariant of the adapted skin temperature (AT), and the intensity of stimulation within the range of stimuli used (from as little as −0.05‡C to as much as −1.25‡C). In view of the characteristics ascribed to the thermosensory apparatus in humans, it is postulated that spatial summation occurs in the central nervous system.

35 citations

Journal ArticleDOI
TL;DR: Spatial and temporal summation have been measured in perimetrically impaired regions of the visual field resulting from lesions in the pre‐geniculate visual pathways and that resulting from post-geniculate lesions (optic radiation and/or striate cortex).
Abstract: 1. Spatial and temporal summation have been measured in perimetrically impaired regions of the visual field. Two classes of impairment have been studied: that resulting from lesions in the pre-geniculate visual pathways, and that resulting from post-geniculate lesions (optic radiation and/or striate cortex). 2. Control measurements were made in the perimetrically normal visual fields of subjects without visual pathway damage. 3. Spatial summation was found altered in all impaired visual fields: the greater the threshold elevation produced by the lesion, the more nearly complete was spatial summation. 4. The above relation between threshold and spatial summation has also been given numerical form. This has been shown to be very nearly identical to the threshold—spatial summation relation which is seen as stimuli are increasingly peripherally presented in normal visual fields. 5. It has been shown that the alterations of spatial summation brought about by a lesion are found only in those parts of the visual field which are perimetrically impaired: spatial summation is always normal in perimetrically normal regions of a visual field, even if other parts of the same field show impairment. 6. Temporal summation has been found altered in visual fields impaired by post-geniculate lesions: the greater the threshold elevation produced by the lesion, the more nearly complete was temporal summation. These changes in temporal summation were found only in perimetrically impaired regions of the field. 7. Temporal summation was normal in visual fields impaired by pregeniculate lesions.

35 citations

Journal ArticleDOI
TL;DR: The purposes of study 1 and study 2 were to examine the influence of exhaustive and non‐exhaustive isometric exercise on temporal summation of heat pain in men and women.

35 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202323
202234
202118
20204
201911
201812